Attrition resistant bulk iron catalysts and processes for preparing and using same

ABSTRACT

An attrition resistant precipitated bulk iron catalyst is prepared from iron oxide precursor and a binder by spray drying. The catalysts are preferably used in carbon monoxide hydrogenation processes such as Fischer-Tropsch synthesis. These catalysts are suitable for use in fluidized-bed reactors, transport reactors, and, especially, slurry bubble column reactors.

[0001] This invention was made with Government support under ContractNo.: DE-FG22-96PC96217 awarded by the U.S. Department of Energy (DOE).The Government has certain rights in this invention.

FIELD OF THE INVENTION

[0002] This invention relates to iron catalysts for carbon monoxidehydrogenation processes such as Fischer-Tropsch synthesis. Morespecifically, the invention relates to bulk iron, i.e., high ironcontent, catalysts that are attrition-resistant, that can be used inslurry bubble column reactors, fluidized-bed reactors, and the like, andto processes for preparing and using these catalysts.

BACKGROUND OF THE INVENTION

[0003] Fischer-Tropsch synthesis (FTS) is a set of reactions by which COand H₂ (syngas) are converted into a wide variety of hydrocarbons [Dry,M. E., Catalysis-Science and Technology, p. 160, (1980); Anderson, R.B., et al., The Fischer-Tropsch synthesis, Academic Press, Inc., NY,(1984)]. This synthesis provides the best means currently available forthe conversion of natural gas and carbonaceous fuels such as coal, coke,and petroleum residue to liquids and chemicals, particularly fuel andpremium waxes. When FTS is used to convert low hydrogen-to-carbon ratiosolid fuels, for reforming of natural gas with CO₂, or for otherfeedstocks producing a syngas relatively lean in hydrogen (H₂/CO≅0.4 to1.0), the use of a catalyst with water gas shift (WGS) activity ishighly preferred in order to generate additional H₂ during the reactionas seen below:

CO+2H₂→(—CH₂—)_(n)+H₂O (FTS)

CO+H₂O→CO₂+H₂ (WGS)

[0004] Iron (Fe) is the preferred catalyst for low H₂/CO ratio syngasover its competitor cobalt (Co) because iron is one of the most activeFTS catalysts that is also active for WGS. Iron is also much lessexpensive than Co and has lower methane selectivity in FTS. For thesereasons, iron FTS catalysts have been the subject of extensive researchfocus; see, for example, Bukur, D. B., et al., Natural Gas ConversionIV, Vol. 107, p. 163, (1997); Jothimurugesan, K., et al., Natural GasConversion V, Studies in Surface Science and Catalysis, Vol. 119, p. 215(1998); Jothimurugesan, K., et al., Catalysis Today, Vol. 58, p. 335,(2000); O'Brien, R. J., et al., Applied Catalysis A: General, Vol. 196,p.173, (2000); and Liaw, S. and Davis, B. H., Topics in Catalysis, Vol.10, p. 133, (2000).

[0005] Because FTS is highly exothermic, efficient heat removal from theFTS reactor is necessary to prevent catalyst deactivation via sinteringand to maintain high catalyst activity and selectivity. A slurry bubblecolumn reactor (SBCR) is the preferred reactor type for FTS. The reactoroperates with fine catalyst particles dispersed in a liquid medium andgas is sparged as fine bubbles from the reactor bottom into the liquid.The preferred liquid medium for FTS is the wax product produced in theFTS reaction itself. The wax provides an efficient heat sink and the gasbubbles provide agitation and allow the heat to be rapidly absorbed anddissipated. SBCRs have relatively simple designs and low initial costswhile still permitting high catalyst and reactor productivity. Otheradvantages of SBCRs for FTS include the ability to use low H₂/CO ratiosyngas and favorable conditions for catalyst regeneration and/or makeup.

[0006] Much recent work related to slurry-phase FTS has focused on usingiron catalysts. These catalysts have been prepared by precipitation toachieve high activity for FTS and high selectivity for liquidhydrocarbon and wax. Alpha (α) is the well-known Anderson-Schulz-Florychain growth parameter and is a measure of a catalyst's ability to makeliquids and waxes while making less gas. A catalyst with an α of 0.9 orhigher and methane selectivity below five percent is preferred for FTS.Bulk iron catalysts, i.e., iron catalysts having an iron content,calculated as Fe₂O₃, exceeding about 50 weight percent (wt. %) preparedby precipitation are preferred catalysts, as compared to bulk ironcatalysts prepared by fusion, or to supported iron catalysts prepared byimpregnation of iron onto a support because of the high activity andselectivity of the precipitated bulk iron catalysts. Preparation ofprecipitated bulk iron catalysts for FTS has been extensively reviewed[Dry, (1980); Anderson (1984); Lang, X., et al., Industrial andEngineering Chemistry Research, Vol. 34, p. 73, (1995)]. They aretypically prepared using iron nitrate as an iron oxide precursor.Copper, (Cu), potassium, (K), and/or SiO₂ are added as reduction,chemical, and textural promoters, respectively. The addition ofpotassium results in a higher α catalyst.

[0007] Catalyst attrition is currently a major obstacle to industrialapplication of precipitated bulk iron catalysts in a SBCR [Bhatt, et al.Proceedings of the 1997 Coal Liquefaction and Solid Fuels ContractorReview Conference, U.S. Department of Energy (DOE), Pittsburgh, Pa., p.41, Sep. 3-4, 1997; Srinivasan, R et al., Fuel Science TechnologyInternational, Vol. 14, p.1337, (1996)]. The non-uniform particles and,especially, the irregular shapes of the catalyst particles produced byprecipitation lead to production of catalyst fines by abrasion duringuse. In turn, attrition of iron catalysts causes (i) plugging offilters, (ii) difficulty in separation of liquid/wax product from thecatalyst, and (iii) steady loss of catalyst fines from the reactors.

[0008] A number of recent patents [Chaudhary, V. R. et al., U.S. Pat.No. 5,744,419 (1998); Gangwal, S. K. and Jothimurugesan, K., U.S. Pat.No. 5,928,980 (1999); Espinoza, R. L. et al., U.S. Pat. No. 5,733,839(1998); Rivas, L. A. et al., U.S. Pat. No. 5,710,093 (1998); Moy D.,U.S. Pat. No. 5,569,635 (1996)] are directed to the preparation and useof attrition-resistant, supported iron and other metal catalysts for FTSand other processes. Although the use of catalyst supports such asalumina (prepared as spheroids by spray drying) can improve catalystattrition resistance, supported iron catalysts are generally limited toan iron oxide content of less than 30 wt. %, and have been found to havemuch lower activity compared to bulk iron catalysts for FTS [Dry,(1980); Anderson, (1984); Bukur, D. B., et al., J. Catalysts, Vol. 29,p. 1588, (1990)]. This is because much less iron is available per unitweight of catalyst. The supports also inhibit the activity of promotersand iron reduction and, thus, reduce catalyst effectiveness.

[0009] Improving the attrition properties of bulk iron catalysts isparticularly difficult because bulk iron catalysts in a FTS SBCR aresubject to both physical attrition and chemical attrition. Physicalattrition can be caused by particle collision with other particles orreactor walls and by rapid sparging of gas around the particles.Chemical attrition can be caused during catalyst pretreatment and/orduring FTS by iron catalyst phase changes (Fe₂O₃→Fe₃O₄→Fe metal and/orFe carbide), resulting in a decrease or complete loss of physicalintegrity of the catalyst particles.

[0010] Although chemical attrition during the pretreatment ofprecipitated bulk iron catalysts and during FTS, is not clearlyunderstood, it is well known that the active iron phase for FTS is aniron carbide [Srivastava, et al., Hydrocarbon Processing, (1990); Rao,V. et al., Fuel Processing Technology, Vol. 30, p. 83, (1992)]. Thecommon pretreatment conditions employed are H₂ reduction, CO reduction,or syngas reduction with the later two resulting in a more active andhigher α catalyst. At least five forms of iron carbides are known toexist; three octahedral-carbides with carbon in the octahedralinterstices, and two trigonal prismatic-carbides with carbon in trigonalprismatic interstices. Although the role of these carbides in FTS is notresolved, the multiplicity of carbide phases and iron oxidation statescan cause grain boundaries to grow during FTS which can placesignificant stresses on the iron particle that can lead to chemicalattrition.

[0011] Spray drying using an appropriate binder is the industrial methodof choice for producing microspheroid (40-120 μm) attrition resistantfluidized catalytic cracking (FCC) catalysts and fluidizable alumina inlarge quantities. It consists of first producing a slurry of catalystprecursor dispersed in a solution of the binder oxide precursor thatwill form the hard phase of the catalyst [Stiles, A. B., CatalystManufacture, Marcel Dekker, Inc., NY, (1983)]. The oxide material mustbe in the form of discrete colloidal particles. The slurry is then spraydried to form “green” microspheres, mostly larger than 40 μm and mostlysmaller than 120 μm that are calcined (heat treated in air) at anappropriate temperature (typically 300-500° C.) to produceattrition-resistant micro-spheroid particles.

[0012] Typically, attrition-resistant particles produced by spray dryingrequire 25 to 50 wt. % binder constituting a continuous framework inwhich are embedded small particles of the active catalyst. Some binderstypically used in industry include colloidal silica, colloidal alumina,kaolin clay, and phosphate-modified clay. Bergna, U.S. Pat. No.4,849,539, (1989); Bergna, U.S. Pat. No. 4,677,084, (1987); and Bergna,H. E. et al., Catalysis Today, 1, p. 49, (1987); disclose a process forproducing spray dried, attrition-resistant vanadium oxide/phosphorousoxide catalysts having a lower binder content, preferably about 10 wt %silica-based binder, wherein the binder is added in the form ofsubcolloidal size particles. During the spray drying process, thesubcolloidal size particles of the binder migrate between the spaces ofthe much larger particles of catalyst or catalyst precursor, to thesurface of the spray dried particles and form a hard peripheralcomposite exterior shell after sintering.

[0013] Past attempts to produce attrition-resistant, precipitated bulkiron FTS catalyst microspheres by spray drying have met with failure[Srinivasan et.al. (1996); Bhatt et al., (1997); O'Brien et al., CoalLiquefaction and Gas Conversion Contractor's Review Conference, DOE,(1995)]. In fact, attrition was so severe for a spray dried, high α ironFTS catalyst prepared by United Catalysts, Inc. that a FTS pilot plantat Laporte, Tex. operated by Air Products for DOE had to shut down afteronly a few hours of testing due to production of catalyst fines andfilter plugging [Private Communication with DOE, (1999)].

[0014] Espinoza et al, PCT Application WO99/49965, (1999) claim thatattrition resistance of precipitated iron FTS catalysts can be increasedsimply by heat treatment at temperatures above 300° C. without the useof spray drying or binders. However, it is well known that nearly allheterogeneous catalysts, including precipitated iron FTS catalysts, arecalcined at 300° C. or higher [Jothimurugesan et al., (1998); Gormley,R. J., et al., Applied Catalysis A: General, Vol. 161, p. 263, (1997)].Espinoza et al. do not present any attrition results of carbided or usedcatalysts. Benham et al, U.S. Pat. No. 5,504,118, (1996) teach thepreparation of a 5 to 50 μm size iron FTS catalyst for slurry-phase FTSby spray drying without the use of binders. However, these catalysts arenot said to be attrition resistant. Thus, such catalyst would notsuitable for a slurry-phase reactor from an attrition standpoint and, inaddition, the catalysts particles in the lower portion of the 5 to 50 μmparticle size range would be likely to plug filters through which wax isremoved from the reactor.

[0015] Thus, despite substantial effort and research, there are nocommercially available precipitated bulk iron FTS catalysts, which areattrition resistant and have substantial catalytic activity.Accordingly, in practice, commercially available precipitated bulk ironcatalysts, such as the standard Ruhrchemie pelletized catalyst, aresupplied in pelletized form and are limited to use in fixed bedreactors. Nevertheless, precipitated bulk iron catalysts remain thepreferred FTS catalysts for low H₂/CO ratio syngas processes due totheir high activity and selectivity.

SUMMARY OF THE INVENTION

[0016] This invention provides attrition resistant bulk iron catalystsfor CO hydrogenation processes such as FTS. The attrition resistant bulkiron catalysts of the invention can be used in slurry bubble columnreactors, fluidized bed reactors, and in other highly abrasiveenvironments without unacceptable attrition. Nevertheless, the attritionresistant bulk iron catalysts of the invention have high activity andselectivity, comparable to or exceeding the activity and selectivity ofconventional pelletized, precipitated bulk iron catalysts, such as theRuhrchemie catalyst. The invention also provides processes for producingattrition resistant bulk iron catalysts and processes for use of thecatalysts.

[0017] The attrition resistant bulk iron catalysts of the invention aresubstantially spherical particles comprising a finely divided ironcomponent such as one or more iron oxides, typically Fe₂O₃, an ironoxide precursor, or an activated form of iron oxide, e.g., iron carbideor elemental iron (iron metal), and a substantially uniform distributionof binder, preferably silica. Advantageously, the iron component ispresent in an amount, calculated as Fe₂O₃, of at least about 50 wt. %,preferably at least about 60 wt. %, more preferably at least about 70wt. %, most preferably about 80 wt. % or higher, based on adjustedcatalyst weight (adjusted as necessary so that the iron component iscalculated as Fe₂O₃). Advantageously, the catalysts of the inventionalso comprise an FTS promoter such as a copper and/or potassium FTSpromoter, or a precursor thereof. Preferably, the binder content of theattrition resistant bulk iron catalysts of the invention is less thanabout 20 wt. %, more preferably between about 8 and about 16 wt. %. Inpreferred embodiments, the attrition resistant bulk iron catalysts ofthe invention have a bulk density exceeding 0.8 grams per cubiccentimeter (g/cm³), more preferably, exceeding 0.8 grams per cubiccentimeter g/cm³. Accordingly the bulk iron catalysts of the inventioncan be more readily separated from hydrocarbon products such as wax,compared to conventional precipitated bulk iron catalysts, which have adensity of about 0.7 g/cm³, about the same as the density of wax.

[0018] According to another aspect, the present invention provides aprocess for producing attrition resistant bulk iron catalysts comprisingthe steps of forming a slurry which comprises a precipitated iron oxideprecursor or its derivative (i.e., an iron oxide derivative or acatalytically activated iron derivative of the iron oxide precursor) anda binder, and spray drying the slurry to form substantially sphericalparticles. Advantageously the precipitated iron oxide precursor or itsderivative comprises at least about 50 wt. %, calculated as Fe₂O₃, ofthe dry solids content of the slurry. Preferably, the spray driedparticles are calcined for a time and at a temperature sufficient toconvert iron oxide precursor to iron oxide, typically at a temperatureexceeding about 200° C., preferably at a temperature exceeding about250° C, more preferably at a temperature exceeding about 275° C.Advantageously the calcined particles are activated by treating thecalcined particles under conditions sufficient to convert iron oxide toa catalytically active iron composition, preferably an iron carbidecontaining composition.

[0019] In one preferred aspect of the invention, the slurry is treatedwith sufficient strong acid to reduce the pH to less than 2.0,preferably to about 1.0 to 1.5 prior to the spray drying step. Apreferred strong acid is nitric acid. In accordance with this aspect ofthe invention, it has been found that reducing the slurry pH to belowabout 2.0, preferably to below about 1.5, before spray dryingsignificantly improves the attrition properties, i.e., reduces theattrition loss, of the bulk iron catalyst of the invention.

[0020] The starting materials for the bulk iron catalyst of theinvention are readily available in commerce. The catalyst of thisinvention has been found capable of providing FTS activity andselectivity that are much higher than supported iron catalysts reportedin the prior art (for example, U.S. Pat. No. 5,928,980). The ironcatalyst according to the present invention can be used because of itshigh attrition resistance in both calcined and carbided forms invirtually any reaction process including FTS, that uses a fluidized-bedreactor, or especially a slurry bubble column reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In the drawings which form a portion of the original disclosureof the invention;

[0022]FIG. 1 is a scanning electron microscope (SEM) photomicrographtaken of the cross section of a single particle having a diameter ofabout 70 μm, of one preferred attrition resistant bulk iron catalyst ofthe invention;

[0023]FIG. 2 is an energy dispersive x-ray spectroscopy (EDXS) SEMphotomicrograph, taken of the cross section of a single particle havinga diameter of about 70 μm, of the same attrition resistant bulk ironcatalyst of the invention as in FIG. 1, and demonstrates thesubstantially uniform distribution of iron in the catalyst particle; and

[0024]FIG. 3 is an EDXS SEM photomicrograph taken of the cross sectionof a single particle having a diameter of about 70 μm, of the sameattrition resistant bulk iron catalyst of the invention as in FIGS. 1and 2, and demonstrates the substantially uniform distribution ofsilicon in the catalyst particle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] In the following detailed description, preferred embodiments ofthe invention are described to enable practice of the invention.Although specific terms are used to describe and illustrate thepreferred embodiments, such terms are not intended as limitations onpractice of the invention. Moreover, although the invention is describedwith reference to the preferred embodiments, numerous variations andmodifications of the invention will be apparent to those of skill in theart upon consideration of the foregoing and following description.

[0026] As used herein, the term “bulk iron” catalysts refers tocatalysts having an average content of an iron component selected fromthe group consisting of iron oxide (Fe₂O₃), an iron oxide precursor, ora catalytically active iron composition which can be derived from ironoxide, typically iron carbide(s) or elemental iron, in an amount of atleast about 50 wt. %, calculated as Fe₂O₃, of the adjusted weight ofcatalyst. “Adjusted weight” of catalysts and slurries used to formcatalysts of the invention, as used herein, refers to the actual weightadjusted as necessary so that the iron component is calculated as Fe₂O₃.Further, unless expressly stated otherwise, all weight percentages ofcatalysts (including “green”, calcined and activated catalysts) andslurries used to prepare the catalysts, are calculated herein such thatthe iron component is calculated as Fe₂O₃, and the total catalyst orsolids weight of the slurry is calculated as adjusted weight.

[0027] The attrition resistant bulk iron catalyst of the invention isprepared by spray drying a slurry which comprises a precipitated ironoxide precursor and a binder. Alternatively, the bulk iron catalyst isprepared by spray drying a slurry comprising an iron oxide derivative ora catalytically activated iron derivative of a precipitated iron oxideprecursor, and a binder. Precipitated iron oxide precursors are wellknown to those skilled in the art and include iron nitrate, preferablyFe(NO₃)₃, iron sulfate, iron chloride, iron acetate and otherorganometallic compounds such as iron carbonyls, and the like.Precipitated iron oxide precursors evidence a significantly highersurface area, as compared to iron oxide precursors prepared by othermethods, as is well know in the art. Iron oxide derivatives ofprecipitated iron oxide precursor are, as is also well known to thoseskilled in the art, the iron oxide compound or compounds (typicallyFe₂O₃) produced by calcining the iron oxide precursor in anoxygen-containing environment. Catalytically activated iron derivativesof precipitated iron oxide precursors are the active iron phase(s)and/or compound(s) for FTS, including iron carbides and/or elementaliron prepared by the pretreatment of FTS iron catalysts, typically viaH₂ reduction, CO reduction, or syngas reduction, as will also beapparent to the skilled artisan. Preferably, the iron component of theslurry used in the process of the present invention is a precipitatediron oxide precursor, and the preferred iron oxide precursor isFe(NO₃)₃.

[0028] Advantageously, at least about 50 wt. % of the dry solids contentof the slurry is made up by the precipitated iron oxide precursor orderivative (iron oxide or catalytically activated iron derivative),calculated as Fe₂O₃. Preferably at least about 60 wt. %, morepreferably, at least about 70 wt. %, most preferably about 80 wt. % ormore, of the dry solids content of the slurry is made up by theprecipitated iron oxide precursor or derivative, calculated as Fe₂O₃.Advantageously, the iron oxide precursor is a wet filtered cakerecovered directly from a precipitation process or step.

[0029] Preferably the slurry also comprises one or more FTS promoters orprecursor(s) thereof. FTS promoters are well known to those skilled inthe art and include chemical promoters such as metals and/or oxidesthereof of Cu, K, Ru, noble metals such as Pt, Mn, and Cr, and texturalpromoters such as SiO₂. The preferred chemical promoters are oxides ofCu, and K. Preferably, the promoters are present in the slurry asprecursors formed by precipitation. It is also preferred that thepromoter precursor(s) be formed in the precipitation step used to formthe iron oxide precursor. SiO₂, when used as a textural promoter, isadded to the slurry as particulate SiO₂ or as a particulate precursor ofSiO₂, preferably prepared by precipitation. The preferred Cu precursoris Cu(NO₃)₂. The preferred K precursor is KHCO₃. The preferred SiO₂precursor is precipitated tetraethylortho-silicate, Si(OC₂ H₅)₄. Theslurry can also include catalyst support materials, if desired, orsubstantially inert fillers, stabilizers, or the like.

[0030] The binder used in the slurry is preferably an oxide binderprecursor dissolved or dispersed in a solvent, preferably water. Inparticular, the oxide precursor consists essentially of an oxideprecursor of subcolloidal particle size. “Subcolloidal particles” (size)are defined herein as particles for which the largest dimension is nogreater than about 5 nm. The particles must not aggregate, precipitateor gel during or following the formation of the binder solution or uponcontact with the catalyst, catalyst precursor or catalyst supportparticles. The subcolloidal particles must provide a sufficiently stablesuspension, i.e., solution, and slurry to permit spray drying. The oxidecan be chosen from the group comprising SiO₂, Al₂O₃, P₂O₅, TiO₂, ZrO₂,MgO, Cr₂O₃, and rare earth oxides. Examples of binder solutions forthese oxides include silicic acid, basic aluminum chloride, phosphoricacid, titanyl oxychloride, hydrolyzed zirconyl nitrate, magnesiumacetate, hydrolyzed basic chromic chloride (Cr(OH)₂Cl₄) and hydrolyzedbasic nitrates of rare earths. The preferred oxide is SiO₂ and thepreferred oxide precursor is silicic acid, especially polysilicic acid.

[0031] The preferred binder includes an SiO₂ precursor comprisingpolysilicic acid (PSA) and water. The PSA is preferably formed fromsodium silicate in a water solution. Such solutions are advantageouslyprepared by diluting a sodium silicate solution with distilled water toyield a relatively high pH of e.g., 11.4, adding a solution acidifierpreferably a strong nuclear sulfonic acid cation exchanger such asDovex® HCR-W2-H resin to bringing the pH down to 1.5 to 2.0. Preparationof such binder solutions is well known to those skilled in the art andis disclosed, for example in U.S. Pat. Nos. 4,849,539, (1989), and4,677,084, (1987) to Bergna, which are hereby incorporated herein byreference.

[0032] In a preferred embodiment of the invention, the slurry is furthertreated with sufficient strong acid to reduce the pH to less than 2.0,preferably to about 1.0 to 1.5. A currently preferred strong acid isnitric acid. Reducing the slurry pH to below about 2.0, preferably tobelow about 1.5, before spray drying has been found to significantlyimprove the attrition properties of the catalyst. It is also preferredthat the binder content of the slurry is less than about 20 wt. %,calculated based on dry solids adjusted weight of the slurry, morepreferably is between about 4 and about 20 wt. %, and even morepreferably is between about 8 and about 16 wt. % of the dry solidsadjusted weight of the slurry.

[0033] The slurry is spray dried using conventional processes andapparatus to form substantially spherical spray dried particles.Preferably the size of the particles is such that at least about 80percent by volume of the particles have a diameter between 40 and 120μm. Conventional spray drying processes and apparatus are well known tothose skilled in the art. The selection of apparatus, and processconditions to achieve the foregoing particle size distribution can bereadily accomplished by a skilled artisan apprised of presentdisclosure. Advantageously the slurry is spray dried at a temperatureabove about 200° C., preferably about 250° C., in a spray drying chamberto form the substantially spherical spray dried particles. Preferable,the slurry has a solids content of between about 10 and about 20 wt. %based on the adjusted weight of the slurry, and thus has a water contentof between about 80 and 90 wt. %.

[0034] Thereafter the spray dried particles are preferably calcined inan oxygen-containing atmosphere to convert the iron oxide precursor andthe promoter precursor to iron oxide and to the promoter, respectively.Typically the calcining temperature exceeds about 200° C., and ispreferably a temperature exceeding about 250° C., more preferably about275° C., or higher, e.g., 300° C. In general it is preferred thatcalcining be conducted at a temperature at least about 25° C. above thereaction temperature of the predetermined catalytic process, such asFTS, for which the catalyst is to used.

[0035] Preferably, the calcined particles are thereafter activated bytreating the calcined particles under conditions sufficient to convertthe iron oxide to a catalytically active composition, such as acomposition containing iron metal or iron carbide, preferably an ironcarbide containing composition. Advantageously this is accomplished byexposing the calcined particles to CO or to a mixture of CO and H₂, at atemperature 270-300° C. and at a pressure of from 0.1 to 0.2 MPa for anextended time, e.g., 12 hours, to carbide the catalyst. The catalyst isthen ready for FTS using syngas or for use in another carbon monoxide orother reducing gas hydrogenation process, such as a water gas shiftreaction. The preferred reducing gases are CO or a mixture of H2 and CO(syngas), with syngas in a H₂ to CO ratio of 0.4 to 1.0 being thepreferred reducing gas.

[0036] In a preferred aspect of the invention, the bulk precipitatediron catalyst is prepared by the steps set forth below.

[0037] Prepare an aqueous solution containing Fe (NO₃)₃ (1.0M) togetherwith Cu(NO₃)₂ (1.0M) that corresponds to a ratio of 100 Fe to 5 Cu andtetraethylorthosilicate that corresponds to a ratio of 100 Fe to 0 to 25SiO₂. Prepare an ammonium hydroxide solution (27M) in a separatecontainer, and pump the two solutions into a well-mixed third containerat controlled flow rate to precipitate the iron oxide precursor andcopper promoter precursor at a pH of 6.2 and room temperature. Theprecipitate is preferably washed with deionized, distilled water andvacuum filtered to remove excess NH₄OH and to prepare a wet cake.

[0038] Prepare a 1 molar solution of KHCO₃ in an amount that correspondsto a ratio of 100 Fe/5 Cu/4.2K and add it to the wet cake.

[0039] Prepare a polysilicic acid (PSA) solution by diluting sodiumsilicate solution with distilled water to yield a pH of 11.4, and addDovex® HCR-W2-H resin to bring the pH down to 3.0. Add a sufficientamount of this PSA solution to the wet cake to give an Fe (calculated inthis case as Fe, only) to SiO₂ ratio ranging from 100/4 to 100/20. Thenadd sufficient concentrated nitric acid to bring the pH down to 1.0-1.5.

[0040] Spray dry the resultant slurry in a 250° C. spray dryer chamberthrough a bottom feed two-fluid nozzle to produce microspheroidalparticles in the 40 to 120 μm range.

[0041] Calcine the spray dried particles in air at 300° C. for fivehours. Load the desired amount of the calcined spray dried catalyst intoa fixed-bed reactor. Pass CO or syngas at 0.1 to 0.2 MPa through thecatalyst and slowly raise the temperature (<2° C./min.) to 280° C. andhold it at that temperature for 12 hours. The catalyst is now activatedand ready for FTS at desired pressure and temperature after transferringit to a desired reactor, preferably a fluidized-bed or slurry bubblecolumn reactor. If desired, the catalyst can be activated ‘in situ’ inthe fluidized-bed or slurry bubble column reactor.

[0042]FIGS. 1-3 are SEM photomicrographs of the cross section of asingle particle having a diameter of about 70 μm, of one preferredattrition resistant bulk iron catalyst of the invention and are alsorepresentative of additional photomicrographs taken of other preferredattrition resistant bulk iron catalyst particles of the invention. Thephotomicrographs of FIGS. 2 and 3 were taken using EDXS to determine thedistribution of iron and silicon, respectively, in the catalystparticles. As can be seen from FIGS. 2 and 3, the attrition resistantbulk iron catalysts of the invention exhibit a substantially uniformdistribution of iron and silicon. Thus, the binder does not migrate tothe surface of the particle as it does in the catalysts produced byBergna in U.S. Pat. Nos. 4,677,084 and 4,849,539; and, R. M., Bergna, H.E. et al., Catalysis Today, 1, p. 49, (1987). Moreover, although, in thecatalyst particles of Bergna, sintering is said to be almost alwaysnecessary, examination of preferred catalyst particles of the inventionfollowing calcining reveals no crystalline silica, indicating thatsintering of the silica binder has not occurred. Also, unlike theprocess used by Bergna, in which the spray drying slurry is preparedusing a dry powder catalyst precursor, in this invention the catalystprecursor is advantageously a wet filtered cake from precipitation.

[0043] Table 1 shows the attrition properties of catalysts of theinvention, which were prepared according to Examples 1-13, set forthhereinafter. Each of these catalysts had a weight ratio of Fe, Cu, and Kof 100 Fe/5 Cu/4.2 K, calculated in this case based on the weights ofthe Fe, Cu, and K, elements only. As mentioned earlier, silica can beadded to the catalyst in two ways, as a particulate in the case of asilica textural promoter, and as a component of the binder solution inthe case of a silica binder. In the catalysts shown in Table 1, silicaadded as a textural promoter in particulate form (typically as aprecipitate from (tetraethyl-orthosilicate) is designated as P(x) wherex is the silica parts by weight that is left in the catalyst aftercalcining. The silica added in a binder solution was typically added aspolysilicic acid is designated as B(y) where y is the weight % SiO₂ thatis left in the catalyst after calcining. TABLE 1 Attrition Measurementsof Catalysts Attrition Loss (%) Air Jet Attrition Volume Moment ASTMMethod Loss (%) (μm) D-5757-95 Jet Cup Jet Cup Test,* % Change SilicaContent Precipitation Slurry One Five Test,* One Hour in Volume Catalyst# Designation pH pH Hour Hours One Hour Before After Moment 27 P(0)/B(4)6.2 6.4 24.4 32.6 26.6 78.0 39.2 49.7 28 P(0)/B(8) 6.2 6.4 25.7 35.421.8 86.7 45.4 45.4 41 P(0)/B(8) 6.2 1.5 6.4 17.7 NM NM NM NM 42P(0)/B(10) 6.2 1.5 5.2 15.5 NM NM NM NM 43 P(0)/B(10) 6.2 1.5 7.6 14.64.8 75.4 57.3 24 30 P(0)/B(12) 6.2 6.4 12.8 22.7 8.5 88.8 67.8 23.6 39P(0)/B(12) 6.2 1.5 4.7 10.0 NM NM NM NM 31 P(0)/B(16) 6.2 6.4 22.0 30.118.2 69.9 47.6 31.9 32 P(0)/B(20) 6.2 6.4 34.9 35.0 51.6 63.5 23.7 62.733 P(5)/B(12) 6.2 6.4 24.2 37.3 26.6 103.0 37.3 63.8 34 P(10)/B(12) 6.26.4 31.0 39.6 33.9 83.0 34.1 58.9 35 P(15)/B(12) 6.2 6.4 42.1 NM 39.690.2 27.7 59.3 36 P(20)/B(12) 6.2 6.4 39.1 NM 41.3 85.9 30.1 64.6Co/Zr/SiO₂ (a) NA NA NM NM 31.1 79.9 45.2 43.5 Co/Ru/Al₂O₃ (b) NA NA NMNM 5.7 75.1 63.7 15.2

[0044] High attrition resistance of a catalyst is a crucial requirementfor operation in a slurry bubble column reactor, and in fluidized bedreactors. In the data shown in Table 1, the attrition was measured usingtwo methods. The first method followed the ASTM D-5757-95 standardmethod. The method is based on fluidizing 50 g of catalyst usinghumidified air passing through three small holes and is described indetail in the ASTM standard. Preferably, the catalysts of the inventionhave an attrition loss after one hour using this method of less than 15wt. %, more preferably, less than 10 wt. %, most preferably less than 8wt. %, based on actual catalyst weight. The second method is based on aproposed ASTM design by Weeks and Dumbill, Oil, and Gas J., Vol. 88, p.38, (1990) and is described in detail by Zhao, Goodwin, and Oukaci,Applied Catalysis A., Vol. 198, p. 99, (1999). The reason to use twomethods was to ensure credibility of the measurements since the twomethods should relatively produce similar attrition characteristics. Jetcup results of two cobalt FTS catalysts found to demonstrate adequateattrition resistance for slurry bubble column reactor use, are alsoincluded in the Table 1 as benchmark.

[0045] In the first method, attrition loss at both 1 hour and 5 hourswas measured. In the second method attrition loss at 1 hour was measuredand the volume moment of sample before and after the test was calculatedbased on before and after particle size distribution. The volume momenthas units of μm and is a mean particle size based on volume.

[0046] The results shown in Table 1 in the table show the following.Reducing the slurry pH to 1.5 before spray drying significantly reducesattrition loss (increases attrition resistance) in catalysts 41, 42, and43. These are the preferred embodiments of the invention. Further theattrition resistance increases with addition of binder silica above 6wt. % and then decreases at additions above 16 wt. %. As will beapparent, the two attrition test methods relatively agree, lendingcredence to the data.

[0047] Table 1 further illustrates that the volume mean particle size ofthe catalysts prepared is typically around 70 to 100 μm.

[0048] In addition, Table 1 shows that Catalyst 43 is equivalent inattrition resistance to the benchmark supported cobalt catalysts thathave been tested in a laboratory slurry bubble column reactor.

[0049] Addition of silica by precipitation as a textural promoter (andnot as a binder), is seen from the data of Table 1 to reduce attritionresistance of the catalyst. Thus, in preferred embodiments of theinvention, addition of particulate silica, e.g., by precipitation, isminimized or avoided. In contrast, conventional precipitated bulk ironcatalysts discussed in the prior art typically include particulatesilica added by precipitation.

[0050] The structural properties of catalysts before and after jet cupattrition tests are shown in Table 2. The surface area of the catalystsafter calcining range from a low of about 60 m²/g to a high of 245 m²/g.In comparison, a standard Ruhrchemie iron catalyst with the same ratioof Fe, Cu, and K as the catalysts of this invention shown in Tables 1and 2, received from the U.S. Department of Energy (DOE), containing 25%silica added by precipitation is included in the table. The surface areaof the catalysts increases as silica content increase. Catalyst 41 to43, the currently preferred embodiments of the invention have lowersurface area than the Ruhrchemie catalyst. As will be shown later, theseare also the preferred catalysts for the FTS reaction. They also havehigher attrition resistance. Thus, contrary to the general belief in theart that surface area increases reactivity, the results here show thatsurface area is not the most important parameter. In fact, the catalystsprepared with a slurry pH of 1.5 for spray drying have lower surfaceareas and yet are the preferred embodiments. TABLE 2 StructuralProperties Silica BET Surface Pore Volume Average Pore Bulk Content Area(m²/g) (cm³/g) Radius (Å) Density Catalyst # Designation Fresh AttritedFresh Attrited Fresh Attrited (g/cm³) 27 P(0)/B(4) 101.3 94.2 0.29 0.2843.6 44.7 NM 28 P(0)/B(8) 124.6 108.1 0.28 0.26 35.3 36.1 NM 41P(0)/B(8) 60.5 NM NM NM NM NM NM 42 P(0)/B(10) 79.8 NM NM NM NM NM NM 43P(0)/B(10) 81.5 NM NM NM NM NM 1.0 30 P(0)/B(12) 146.2 137.1 0.28 0.2932.0 37.7 NM 39 P(0)/B(12) 107.8 NM NM NM NM NM NM 31 P(0)/B(16) 176.6173.1 0.37 0.34 33.8 33.3 NM 32 P(0)/B(20) 158.3 168.2 0.33 0.34 37.337.7 NM 33 P(5)/B(12) 179.4 180.5 0.34 0.34 35.2 35.8 34 P(10)/B(12)190.8 177.1 0.37 0.35 36.9 37.3 0.89 35 P(15)/B912) 216.8 188.7 0.360.33 30.8 33.4 0.95 36 P(20)/B(12) 245.0 243.9 0.39 0.40 30.2 32.6 0.92Ruhrchemie P(25) 300 NM NM NM NM NM NM

[0051] The data set forth in Table 2 further shows that attrition in thejet cup does not cause the pore structure to collapse as minimal changewithin the error of the measurement is generally seen in the structuralproperties. The bulk density of catalyst is around 0.9 to 1.0 g/cm³.This is a preferred density since it is much higher than wax (density≅0.68) and would allow easy separation of the catalyst from the wax. Incontrast, typical precipitated catalysts have a density of ≅0.7 g/cm³making them difficult to separate from the wax.

[0052] Table 3 sets forth the attrition resistance of catalysts of thepresent invention following calcining to convert the iron precursor toiron oxide, as compared to the attrition resistance of the same catalystfollowing activation to convert the iron oxide to a carbided form.Catalyst carbiding was performed by passing CO through a bed of catalystat 280° C. The catalyst was heated to this temperature in flowing CO ata heating rate of 1° C./min and then exposed to CO at 280° C. for 12hours. This is typically how a catalyst is activated prior to use forFTS. For prior conventional catalysts tested by other researchers, ithas been shown that carbided catalysts have drastically lower attritionresistance because carbide (χ-Fe_(2.5)C) formation causes grainboundaries to grow, thus creating very small particles that can breakoff. In contrast, as seen in Table 3, the catalysts prepared in thisinvention generally show equal or better attrition resistance incarbided form. TABLE 3 Attrition Measurements of Fresh and CarbidedCatalysts Silica Attrition Loss (%) Volume Moment Content Jet CupMethod* Fresh Attrited Carbided Attrited (% Catalyst # Designation FreshCarbided (μm) (% of fresh) (μm) of carbided) 27 P(0)/B(4) 26.6 NM 78.050.3 NM NM 28 P(0)/B(8) 21.8 21.8 86.7 52.4 77.9 46.9 43 P(0)/B(10) 4.87.7 75.4 76.0 72.7 70.2 30 P(0)/B(12) 8.5 NM 88.8 76.4 82.6 NM 31P(0)/B(16) 18.2 15.6 69.9 68.1 61.1 65.4 32 P(0)/B(20) 51.6 NM 63.5 37.3NM NM 33 P(5)/B(12) 26.6 13.2 103.0 36.2 86.7 48.3 34 P(10)/B(12) 33.9NM 83 41.1 NM NM 35 P(10)/B(12) 39.6 NM 90.2 30.7 NM NM 36 P(10)/B(12)41.3 NM 85.9 35.4 70.0 46.9 Co/Zr/SiO₂ (a) 31.1 NA 79.9 56.5 NA NA

[0053] Tables 4, 5, and 6 show FTS results for the catalysts. The datain Table 4 was obtained using a 1-g fixed-bed microreactor. The calcinedcatalyst was heated in flowing CO to 280° C. at 0.1 MPa and held at thattemperature for 16 hours. This pre-treatment was followed by reductionof the temperature to 270° C. and syngas was then started at theconditions shown. All of the FTS tests were conducted for 100-150 hoursand the catalysts showed no decline in activity over this period oftesting. All of the catalysts prepared by this invention had higheractivity than the benchmark Ruhrchemie catalyst. The α values of thecatalysts ranged from 0.87 to 0.91. The selectivity varied with silicaaddition method and content. There was a beneficial effect of silicaaddition using polysilicic acid up to 8 to 12 wt % on selectivity(reduced methane, nearly constant C₅+). However, as the PSA silicaincreased above 12 wt. %, the C₁ and C₂ to C₄ selectivities increased atthe expense of C₅+ selectivity. Addition of silica to the catalyst byprecipitation caused an increase in C₁ to C₁₁ fraction. However, C₅ toC₁₁ fraction was higher when silica was added by precipitation. Thissuggests that the catalysts of the invention can be tailored using thesilica content to maximize either the diesel (C₁₀-C₂₀) or the gasolinerange (C₅-C₁₁). The best performance was obtained for Catalyst 43. Ithad the lowest methane selectivity and nearly the highest CO conversion.Catalyst 43 showed 95% conversion over 125h of testing at 270° C., 1.48MPa, 2NL/g cat/h and had less than 4% methane in the hydrocarbonfraction. TABLE 4 Fischer-Tropsch Synthesis Results (1 g fixed-bedreactor, 1.48 MPa, 270° C., 2NL/g · cat/h, Syngas-H₂/CO = 0.67, Ar = 5%)Product Hydrocarbon Silica Content CO Distribution (wt. %) Catalyst #Designation Conversion (%) CH₄ C₂-C₄ C₅-C₁₁ C₁₂+ α 27 P(0)/B(4) 94.3 7.418.1 12.7 61.8 0.92 28 P(0)/B(8) 94.1 6.8 17.6 13.0 62.5 0.91 43P(0)/B(10) 95.0 3.9 17.7 23.8 54.6 0.90 30 P(0)/B(12) 94.3 6.8 19.6 12.860.8 0.89 31 P(0)/B(16) 95.5 9.9 25.0 17.3 47.8 0.87 32 P(0)/B(20) 94.59.6 23.5 17.6 49.3 0.87 33 P(5)/B(12) 95.5 8.8 23.2 22.0 46.0 0.87 34P(10)/B(12) 94.4 10.2 23.5 26.5 39.8 0.86 35 P(15)/B(12) 90.1 10.2 22.430.5 36.9 0.87 36 P(20)/B(12) 88.2 9.5 20.1 32.8 37.7 0.88 RuhrchemieP(25) 86.0 8.3 21.3 14.3 56.1 0.90

[0054] TABLE 5 Fischer-Tropsch Synthesis Results for Catalyst 43 (3 gfixed-bed reactor diluted with 9 ccα-alumina, 2.0 MPa, 6000 scc/cc/h,syngas-H₂/CO = 0.67, N₂ + Ar = 59%) CO CO Oil + Wax TemperatureConversion Productivity Selectivity (mol %) (C₁₀-C₆₀) C₁₀-C₂₀ (° C.)(mol %) (scc/cc/h) CH₄ CO₂ C₂+ g/cc cat/h (wt. %) α 231 24.0 350 4.036.0 60 0.07 13.6 0.95 250 45.0 670 3.5 39.5 57 0.13 17.1 0.94 268 51.0750 4.5 41.5 54 0.10 NM NM

[0055] TABLE 6 Fischer-Tropsch Synthesis Results for Catalyst 43 in aSlurry Reactor* (space velocity = 2300 scc/cc cat/h) Run 1 Run 2 CSTRStirrer Speed (rev/min) 1000 500 Temperature (° C.) 230 260 Pressure(MPa) 1.46 2.1 Run Time (h) 300 300 CO Conversion (mol %) 30 70 COProductivity (scc/cc/h) 350 850 Selectivity CH₄ 1.1 2.0 (%) C₂-C₄ 1.21.8 CO₂ 48 48 C₅+ 49.7 48.2 Oil + Wax (cc/cc cat/h) 0.1 0.13 Water(cc/cc cat/h) 0.022 0.008 α 0.94 NM

[0056] Catalyst 43 was further tested in a larger fixed-bed reactor anda slurry reactor. These results are shown in Tables 5 and 6,respectively. The results in Table 5 were obtained using a deepfixed-bed consisting of 3 cm³ of catalyst mixed with 9 cm³ of inertα-alumina. The dilution was done to prevent overheating during theexothermic FTS reaction. The catalyst was activated using a 0.67 to 1.0H₂ to CO ratio syngas rather than pure CO as in Table 4. The activationprocedure consisted of heating the catalyst at 0.1 MPa from 50° C. to280° C. at 0.5° C./min and holding it at 280° C. for 12 hours. Thecatalyst was then cooled to 100° C. and pressurized to 2.0 MPa inflowing syngas consisting of 41% H₂+CO (H₂/CO=0.67) and balance N₂+Ar.The syngas was flowed at 6000 scc/cc catalyst/h through the bed and thebed was heated to 180° C. at 2° C./min and then heated from 180° C. toreaction temperature at 0.5° C./h. The synthesis was conducted at threetemperatures for 800 hours. The catalyst showed highly stable activityand selectivity and a much higher α=0.94-0.95 compared to Table 3results. This is attributed to syngas activation as opposed to COactivation. The results show low CH₄ selectivity and high C₂+selectivity. The catalyst also shows high WGS activity evidenced by thehigh CO₂ selectivity.

[0057] Finally, slurry reactor results are presented in Table 6. Tworuns of 300h duration each were conducted in a 500cc continuous stirredtank reactor (CSTR). The catalyst was reduced in syngas as describedbefore and then transferred to the reactor in wax. The first test wasconducted at 1000-RPM stirrer speed whereas the second at 500-RPMstirrer speed. Following the 300-hour tests, the catalyst-wax mixturewas examined. The catalyst was found to quickly settle when a sample ofthe mixture was heated in hexane to 50° C. Thus, catalyst-wax separationcould be easily accomplished. Products were continuously withdrawn fromthe reactor in the second run through a 5 μm sintered metal filter,which did not plug, indicating the absence of fines even at such harshRPM conditions. These conditions are more severe than a commercialslurry bubble column reactor (SBCR) and, yet the catalyst was able towithstand the conditions. Thus, the catalyst is deemed suitable for SBCRuse; the first ever-attrition resistant precipitated iron catalystproduced that the inventors are aware of. The fixed-bed and slurryreactor results are in general agreement as seen in Tables 5 and 6. Inthe slurry reactor, a much lower methane selectivity was observed. Theseresults demonstrate that high attrition resistance, high activity, andhigh selectivity to desirable C₂+ products can be achieved in a bulkiron catalyst prepared according to the present invention for FTS. Thefollowing examples describe the catalyst preparation steps and resultsfor specific catalysts.

EXAMPLE 1 Catalyst 27

[0058] This example describes the preparation and testing of theCatalyst 27 [100Fe/5Cu/4.2K containing 4% binder SiO₂ by weight] of theinvention. The preparation comprises the following steps: synthesis ofcatalyst precursor, spray drying of the catalyst precursor andcalcination.

[0059] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0-M solution containing Fe (NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O in the desired Fe/Cu atomic ratio, which was precipitatedby adding aqueous ammonium hydroxide solution. The resulting precipitatewas then filtered and washed three times with deionized water. Thepotassium promoter was added as aqueous KHCO₃ solution to the undried,reslurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in a ratio to produce a final catalystcomposition having 4 wt % SiO₂. The pH of the slurry was 6.4 beforespray drying. A 3 feet diameter×6 feet high Niro Inc. spray dryer wasused to spray-dry the slurry to produce a particle size distributionwith an average size of 70 microns. Finally, the spray-dried catalystwas calcined in an oxygen-containing atmosphere for 5 hours at 300° C.

[0060] The surface area of the calcined catalyst was 101.3 m²/g. The 1hour and 5 hours attrition losses of the calcined catalysts were foundto be 24.4 and 32.6 wt %, respectively, using ASTM method D-5757-95. F-Treaction studies over 100h of testing at 270° C., 1.48 MPa, and 2NL/g-cat/h showed that this catalyst maintained around 94% CO conversionwith a methane selectivity of less than 8 wt % and a C₅+ selectivity ofgreater than 75 wt. %.

EXAMPLE 2 Catalyst 28

[0061] This example describes the preparation and testing of theCatalyst 28 [100Fe/5Cu/4.2K containing 8% binder SiO₂ by weight] of theinvention. The preparation comprises the following steps: synthesis ofcatalyst precursor, spray drying of the catalyst precursor andcalcination.

[0062] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0-M solution containing Fe (NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O in the desired Fe/Cu atomic ratio, which was precipitatedby adding aqueous ammonium hydroxide solution. The resulting precipitatewas then filtered and washed three times with deionized water. Thepotassium promoter was added as aqueous KHCO₃ solution to the undried,reslurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in a ratio to produce a final catalystcomposition having 8 wt % SiO₂. The pH of the slurry was 6.4 beforespray drying. A 3 feet diameter×6 feet high Niro Inc. spray dryer wasused to spray-dry the slurry to produce a particle size distributionwith an average size of 70 microns. Finally, the spray-dried catalystwas calcined in an oxygen-containing atmosphere for 5 hours at 300° C.

[0063] The surface area of the calcined catalyst was 124.6 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts were found tobe 25.7 and 35.4 wt %, respectively, using ASTM method D-5757-95. F-Treaction studies over 100 h of testing at 270° C., 1.48 MPa, and 2NL/g-cat/h showed that this catalyst maintained around 94% CO conversionwith a methane selectivity of less than 7 wt % and a C₅+ selectivity ofgreater than 76 wt %.

EXAMPLE 3 Catalyst 30

[0064] This example describes the preparation and testing of theCatalyst 30 [100Fe/5Cu/4.2K containing 12% binder SiO₂ by weight] of theinvention. The preparation comprises the following steps: synthesis ofcatalyst precursor, spray drying of the catalyst precursor andcalcination.

[0065] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0-M solution containing Fe (NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O in the desired Fe/Cu atomic ratio, which was precipitatedby adding aqueous ammonium hydroxide solution. The resulting precipitatewas then filtered and washed three times with deionized water. Thepotassium promoter was added as aqueous KHCO₃ solution to the undried,reslurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in a ratio to produce a final catalystcomposition having 12 wt % SiO₂. The pH of the slurry was 6.4 beforespray drying. A 3 feet diameter×6 feet high Niro Inc. spray dryer wasused to spray-dry the slurry to produce a particle size distributionwith an average size of 70 microns. Finally, the spray-dried catalystwas calcined in an oxygen-containing atmosphere for 5 hours at 300° C.

[0066] The surface area of the calcined catalyst was 146.2 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts was found tobe 12.8 and 22.7 wt %, respectively, using ASTM method D-5757-95. F-Treaction studies over 100h of testing at 270° C., 1.48 MPa, and 2NL/g-cat/h showed that this catalyst maintained around 95% CO conversionwith a methane selectivity of less than 7 wt % and a C₅+ selectivity ofgreater than 74 wt. %.

EXAMPLE 4 Catalyst 31

[0067] This example describes the preparation and testing of theCatalyst 31 [100Fe/5Cu/4.2K containing 16% binder SiO₂ by weight] of theinvention. The preparation comprises the following steps: synthesis ofcatalyst precursor, spray drying of the catalyst precursor andcalcination.

[0068] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0-M solution containing Fe (NO3)₃.9H₂O and Cu(NO₃)₃2.5H₂O in the desired Fe/Cu atomic ratio, which was precipitatedby adding aqueous ammonium hydroxide solution. The resulting precipitatewas then filtered and washed three times with deionized water. Thepotassium promoter was added as aqueous KHCO₃ solution to the undried,reslurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in a ratio to produce a final catalystcomposition having 16 wt % SiO₂. The pH of the slurry was 6.4 beforespray drying. A 3 feet diameter×6 feet high Niro Inc. spray dryer wasused to spray-dry the slurry to produce a particle size distributionwith an average size of 70 microns. Finally, the spray-dried catalystwas calcined in an oxygen-containing atmosphere for 5 hours at 300° C.

[0069] The surface area of the calcined catalyst was 176.6 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts were found tobe 22 and 30.1 wt %, respectively, using ASTM method D-5757-95. F-Treaction studies over 100h of testing at 270° C., 1.48 MPa, and 2NL/g-cat/h showed that this catalyst maintained around 95% CO conversionwith a methane selectivity of less than 10 wt % and a C₅+ selectivity ofgreater than 65 wt. %.

EXAMPLE 5 Catalyst 32

[0070] This example describes the preparation and testing of theCatalyst 32 [100Fe/5Cu/4.2K containing 20% binder SiO₂ by weight] of theinvention. The preparation comprises the following steps: synthesis ofcatalyst precursor, spray drying of the catalyst precursor andcalcination.

[0071] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0-M solution containing Fe (NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O in the desired Fe/Cu atomic ratio, which was precipitatedby adding aqueous ammonium hydroxide solution. The resulting precipitatewas then filtered and washed three times with deionized water. Thepotassium promoter was added as aqueous KHCO₃ solution to the undried,reslurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in a ratio to produce a final catalystcomposition having 20% SiO₂ binder. The pH of the slurry was 6.4 beforespray drying. A 3 feet diameter×6 feet high Niro Inc. spray dryer wasused to spray-dry the slurry to produce a particle size distributionwith an average size of 70 microns. Finally, the spray-dried catalystwas calcined in an oxygen-containing atmosphere for 5 hours at 300° C.

[0072] The surface area of the calcined catalyst was 158.3 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts was found tobe 34.9 and 35 wt. %, respectively, using ASTM method D-5757-95. F-Treaction studies over 100 h of testing at 270° C., 1.48 MPa, and 2NL/g-cat/h showed that this catalyst maintained around 95% CO conversionwith a methane selectivity of less than 10 wt % and a C₅+ selectivity ofgreater than 67 wt %.

EXAMPLE 6 Catalyst 33

[0073] This example describes the preparation and testing of theCatalyst 33 [100Fe/5Cu/4.2K containing 12% binder SiO₂ by weight and 5parts by weight of precipitated silica] of the invention. Thepreparation comprises the following steps: synthesis of catalystprecursor, spray drying of the catalyst precursor and calcination.

[0074] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0 M solution containing Fe (NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O, Si(OC₂H₅)₅ in the desired Fe/Cu/Si ratio, which wasprecipitated by adding aqueous ammonium hydroxide solution. Theresulting precipitate was then filtered and washed three times withdeionized water. The potassium promoter was added as aqueous KHCO₃solution to the undried, reslurried Fe/Cu precipitate. This catalystprecursor was then slurried with polysilicic acid solution in a ratio toproduce a final catalyst composition having 12 wt. % binder and 5 partsby weight precipitated SiO₂. The pH of the slurry was 6.4 before spraydrying. A 3 feet diameter×6 feet high Niro Inc. spray dryer was used tospray-dry the slurry to produce a particle with an average size of 70microns. Finally, the spray-dried catalyst was calcined in anoxygen-containing atmosphere for 5 hours at 300° C.

[0075] The surface area of the calcined catalyst was 179.4 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts was found tobe 24.2 and 37.3 wt %, respectively, using ASTM method D-5757-95. F-Treaction studies over 100h of testing at 270° C., 1.48 MPa, and 2NL/g-cat/h showed that this catalyst maintained around 95% CO conversionwith a methane selectivity of less than 9 wt % and a C₅+ selectivity ofgreater than 68 wt. %.

EXAMPLE 7 Catalyst 34

[0076] This example describes the preparation and testing of theCatalyst 34 [100Fe/5Cu/4.2K containing 12% binder SiO₂ by weight and 10parts by weight of precipitated SiO₂] catalyst of the invention. Thepreparation comprises the following steps: synthesis of catalystprecursor, spray drying of the catalyst precursor and calcination.

[0077] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0 M solution containing Fe(NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O, Si(OC₂H₅)₅ in the desired Fe/Cu/Si ratio, which wasprecipitated by adding aqueous ammonium hydroxide solution. Theresulting precipitate was then filtered and washed three times withdeionized water. The potassium promoter was added as aqueous KHCO₃solution to the undried, reslurried Fe/Cu precipitate. This catalystprecursor was then slurried with polysilicic acid solution in a ratio toproduce a final catalyst composition having 12% binder SiO₂ by weight 10parts by weight precipitated SiO₂. The pH of the slurry was 6.4 beforespray drying. A 3 feet diameter×6 feet high Niro Inc. spray dryer wasused to spray-dry the slurry to produce a particle size distributionwith an average size of 70 microns. Finally, the spray-dried catalystwas calcined in an oxygen-containing atmosphere for 5 hours at 300° C.

[0078] The surface area of the calcined catalyst was 190.8 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts were found tobe 31 and 39.6 wt %, respectively in a standard 3-hole tester. F-Treaction studies over 100h of testing at 270° C., 1.48 MPa, and 2NL/g-cat/h showed that this catalyst maintained around 94% CO conversionwith a methane selectivity of less than 10 wt % and a C₅+ selectivity ofgreater than 66 wt. %.

EXAMPLE 8 Catalyst 35

[0079] This example describes the preparation and testing of theCatalyst 35 [100Fe/5Cu/4.2K containing 12% binder SiO₂ by weight and 15parts by weight precipitated SiO2] of the invention. The preparationcomprises the following steps: synthesis of catalyst precursor, spraydrying of the catalyst precursor and calcination.

[0080] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0 M solution containing Fe(NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O, Si(OC₂H₅)₅ in the desired Fe/Cu/Si ratio, which wasprecipitated by adding aqueous ammonium hydroxide solution. Theresulting precipitate was then filtered and washed three times withdeionized water. The potassium promoter was added as aqueous KHCO₃solution to the undried, reslurried Fe/Cu precipitate. This catalystprecursor was then slurried with polysilicic acid solution in a ratio toproduce a final catalyst composition having 12 wt % SiO₂. The pH of theslurry was 6.4 before spray drying. A 3 feet diameter×6 feet high NiroInc. spray dryer was used to spray-dry the slurry to produce a particlesize distribution with an average size of 70 microns. Finally, thespray-dried catalyst was calcined in an oxygen-containing atmosphere for5 hours at 300° C.

[0081] The surface area of the calcined catalyst was 216.8 m²/g. The 1hour attrition loss of the calcined catalyst was found to be 42.1 wt %,respectively, using ASTM method D-5757-95. F-T reaction studies over100h of testing at 270° C., 1.48 MPa, and 2 NL/g-cat/h showed that thiscatalyst maintained around 90% CO conversion with a methane selectivityof less than 10 wt % and a C₅+ selectivity of greater than 67 wt. %.

EXAMPLE 9 Catalyst 36

[0082] This example describes the preparation and testing of theCatalyst 36 [100Fe/5Cu/4.2K containing 12% binder SiO₂ by weight and 20parts by weight precipitated SiO₂] of the invention. The preparationcomprises the following steps: synthesis of catalyst precursor, spraydrying of the catalyst precursor and calcination.

[0083] The catalyst precursor was prepared by co-precipitation at aconstant pH of 7.0 using 1.0 M solution containing Fe(NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O, Si(OC₂H₅)₅ in the desired Fe/Cu/Si ratio, which wasprecipitated by adding aqueous ammonium hydroxide solution. Theresulting precipitate was then filtered and washed three times withdeionized water. The potassium promoter was added as aqueous KHCO₃solution to the undried, reslurried Fe/Cu precipitate. This catalystprecursor was then slurried with polysilicic acid solution in a ratio toproduce a final catalyst composition having 12% binder SiO₂ by weightand 20 parts by weight precipitated SiO₂. The pH of the slurry was 6.4before spray drying. A 3 feet diameter×6 feet high Niro Inc. spray dryerwas used to spray-dry the slurry to produce a particle size distributionwith an average size of 70 microns. Finally, the spray-dried catalystwas calcined in an oxygen-containing atmosphere for 5 hours at 300° C.

[0084] The surface area of the calcined catalyst was 245 m²/g. The 1hour attrition loss of the calcined catalysts were found to be 39.1 wt%, respectively, using ASTM method D-5757-95. F-T reaction studies over100 h of testing at 270° C., 1.48 MPa, and 2 NL/g-cat/h showed that thiscatalyst maintained around 90% CO conversion with a methane selectivityof less than 10 wt % and a C₅+ selectivity of greater than 70 wt %.

EXAMPLE 10 Catalyst 39

[0085] This example describes the preparation and testing of theCatalyst 39 [100Fe/5Cu/4.2K containing 12% binder SiO₂ by weight] of theinvention. The preparation comprises the following steps: synthesis ofcatalyst precursor, spray drying of the catalyst precursor andcalcination.

[0086] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0-M solution containing Fe(NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O in the desired Fe/Cu atomic ratio, which was precipitatedby adding aqueous ammonium hydroxide solution. The resulting precipitatewas then filtered and washed three times with deionized water. Thepotassium promoter was added as aqueous KHCO₃ solution to the undried,reslurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in a ratio to produce a final catalystcomposition having 12% binder wt % SiO₂. The pH of the slurry was 6.4.Then nitric acid was added to the slurry to reduce the pH to 1.5. A 3feet diameter×6×feet high Niro Inc. spray dryer was used to spray-drythe slurry to produce a particle size distribution with an average sizeof 70 microns. Finally, the spray-dried catalyst was calcined in anoxygen-containing atmosphere for 5 hours at 300° C.

[0087] The surface area of the calcined catalyst was 107.8 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts was found tobe 4.7 and 10.0%, respectively, using ASTM method D-5757-95.

EXAMPLE 11 Catalyst 41

[0088] This example describes the preparation and testing of theCatalyst 41 [100Fe/5Cu/4.2K containing 8% binder SiO₂ by weight] of theinvention. The preparation comprises the following steps: synthesis ofcatalyst precursor, spray drying of the catalyst precursor andcalcination.

[0089] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0-M solution containing Fe(NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O in the desired Fe/Cu atomic ratio, which was precipitatedby adding aqueous ammonium hydroxide solution. The resulting precipitatewas then filtered and washed three times with deionized water. Thepotassium promoter was added as aqueous KHCO₃ solution to the undried,reslurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in ratios to produce a final catalystcomposition having 8 wt % SiO₂. The pH of the slurry was 6.4. Thennitric acid was added to the slurry to reduce the pH to 1.5. A 3 feetdiameter×6 feet high Niro Inc. spray dryer was used to spray-dry theslurry to produce a particle size distribution with an average size of70 microns. Finally, the spray-dried catalyst was calcined in anoxygen-containing atnosphere for 5 hours at 300° C.

[0090] The surface area of the calcined catalyst was 60.5 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts were found tobe 6.4 and 17.7%, respectively, using ASTM method D-5757-95.

EXAMPLE 12 Catalyst 42

[0091] This example describes the preparation and testing of theCatalyst 42 [100Fe/5Cu/4.2K containing 10% binder SiO₂ by weight] of theinvention. The preparation comprises the following steps: synthesis ofcatalyst precursor, spray drying of the catalyst precursor andcalcination.

[0092] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0-M solution containing Fe(NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O in the desired Fe/Cu atomic ratio, which was precipitatedby adding aqueous ammonium hydroxide solution. The resulting precipitatewas then filtered and washed three times with deionized water. Thepotassium promoter was added as aqueous KHCO₃ solution to the undried,reslurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in a ratio to produce a final catalystcomposition having 10 wt % SiO₂. The pH of the slurry was 6.4. Thennitric acid was added to the slurry to reduce the pH to 1.5. A 3 feetdiameter×6 feet high Niro Inc. spray dryer was used to spray-dry theslurry to produce a particle size distribution with an average size of70 microns. Finally, the spray-dried catalyst was calcined in anoxygen-containing atmosphere for 5 hours at 300° C.

[0093] The surface area of the calcined catalyst was 79.8 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts were found tobe 5.2 and 15.5%, respectively, using ASTM method D-5757-95. F-Treaction studies over 100h of testing at 270° C., 1.48 MPa, and 2NL/g-cat/h showed that this catalyst maintained around 82% CO conversionwith a methane selectivity of less than 5 wt % and a C₅+ selectivity ofgreater than 83 wt. %.

EXAMPLE 13 Catalyst 43

[0094] This example describes the preparation and testing of theCatalyst 43 [100Fe/5Cu/4.2K containing 10% binder SiO₂ by weight] of theinvention. The preparation comprises the following steps: synthesis ofcatalyst precursor, spray drying of the catalyst precursor andcalcination.

[0095] The catalyst precursor was prepared by co-precipitation at aconstant pH of 6.2 using 1.0-M solution containing Fe(NO₃)₃.9H₂O and Cu(NO₃)₃2.5H₂O in the desired Fe/Cu atomic ratio, which was precipitatedby adding aqueous ammonium hydroxide solution. The resulting precipitatewas then filtered and washed three times with deionized water. Thepotassium promoter was added as aqueous KHCO₃ solution to the undried,reslurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in a ratio to produce a final catalystcomposition having 10 Wt % SiO₂. The pH of the slurry was 6.4. Thennitric acid was added to the slurry to reduce the pH to 1.5. A 3 feetdiameter×6 feet high Niro Inc. spray dryer was used to spray-dry theslurry to produce a particle size distribution with an average size of70 microns. Finally, the spray-dried catalyst was calcined in anoxygen-containing atmosphere for 5 hours at 300° C.

[0096] The surface area of the calcined catalyst was 81.5 m²/g. The 1hour and 5 hours attrition loss of the calcined catalysts were found tobe 7.6 and 14.6%, respectively, using ASTM method D-5757-95. F-Treaction studies over 100h of testing at 270° C., 1.48 MPa, and 2NL/g-cat/h showed that this catalyst maintained around 95% CO conversionwith a methane selectivity of less than 4 wt % and a C₅+ selectivity ofgreater than 78 wt. %.

[0097] As can be seen from the foregoing examples and Tables 1 through6, bulk iron catalysts according to the present invention, can beprepared with high attrition resistance in both calcined and carbidedstates. The catalysts also exhibit very high activity and low methaneselectivity, which is required for a commercial FTS process. The longFTS runs in the CSTR demonstrate that the catalyst can withstandconditions in a SBCR, which is the preferred reactor for commercialapplication.

[0098] The invention has been described in considerable detail withreference to various preferred embodiments. However, numerous variationsand modifications can be made without departing from the spirit andscope of the invention as described in the foregoing specification andclaims.

1. An attrition resistant bulk iron catalyst comprising: substantiallyspherical particles, said particles comprising a finely divided ironcomponent and a substantially uniformly distributed binder, said ironcomponent being selected from the group consisting of iron oxideprecursors, iron oxide derivatives of said iron oxide precursors andcatalytically activated iron derivatives of said iron oxide precursors,said iron component being present in an amount, calculated as Fe₂O₃, ofat least 50 wt. %, said catalyst having an attrition loss after one houras determined by ASTM D-5757-95 of less than about 15 wt. % based onactual catalyst weight.
 2. The attrition resistant bulk iron catalyst ofclaim 1 wherein said binder comprises silica.
 3. The attrition resistantbulk iron catalyst of claim 1 wherein said binder is derived from abinder oxide precursor of subcolloidal particle size.
 4. The attritionresistant bulk iron catalyst of claim 1 wherein said catalystadditionally comprises a copper and/or potassium FTS promoter or aprecursor thereof.
 5. The attrition resistant bulk iron catalyst ofclaim 1 wherein said binder comprises less than about 20 wt. % of saidcatalyst.
 6. The attrition resistant bulk iron catalyst of claim 1wherein said binder comprises between about 8 and about 16 wt. % of saidcatalyst.
 7. The attrition resistant bulk iron catalyst of claim 1wherein said catalyst has a bulk density exceeding about 0.8 g/cm³. 8.The attrition resistant bulk iron catalyst of claim 1 wherein said ironcomponent is present in an amount, calculated as Fe₂O₃, of at leastabout 70 wt. %.
 9. The attrition resistant bulk iron catalyst of claim 1wherein said iron component is present in an amount, calculated asFe₂O₃, of at least 80 wt. %.
 10. The attrition resistant bulk ironcatalyst of claim 8 wherein said binder comprises silica.
 11. Theattrition resistant bulk iron catalyst of claim 1 wherein said bindercomprises between about 8 and about 16 wt. % of said catalyst.
 12. Aprocess for producing an attrition resistant bulk iron catalystcomprising the steps: forming a slurry having a solids contentcomprising a finely divided iron component and a binder, said ironcomponent being selected from the group consisting of iron oxideprecursors, iron oxide derivatives of said iron oxide precursors andcatalytically activated iron derivatives of said iron oxide precursors,said iron component being present in an amount, calculated as Fe₂O₃, ofat least 50 wt. % of said solids content of said slurry; and, spraydrying the slurry to form spray dried particles.
 13. A process forproducing an attrition resistant bulk iron catalyst according to claim12 wherein said binder comprises polysilicic acid.
 14. A process forproducing an attrition resistant bulk iron catalyst according to claim12 wherein said iron component comprises said iron oxide precursor. 15.A process for producing an attrition resistant bulk iron catalystaccording to claim 14 further comprising the step of calcining saidspray dried particles for a time and at a temperature sufficient toconvert the iron oxide precursor to iron oxide.
 16. A process forproducing an attrition resistant bulk iron catalyst according to claim15 wherein said polysilicic is present in said slurry in an amountsufficient to provide a binder content of less than about 20 wt. %following said calcining step.
 17. A process for producing an attritionresistant bulk iron catalyst according to claim 12 wherein the slurry istreated with sufficient strong acid to reduce the pH to less than 2.0prior to the spray drying step.
 18. A process for producing an attritionresistant bulk iron catalyst according to claim 17 wherein the slurry istreated with sufficient strong acid to reduce the pH to between about1.0 and 1.5 prior to the spray drying step.
 19. A process for producingan attrition resistant bulk iron catalyst according to claim 17 whereinsaid strong acid is nitric acid.
 20. A process for producing anattrition resistant bulk iron catalyst according to claim 18 whereinsaid strong acid is nitric acid.
 21. A process for producing anattrition resistant bulk iron catalyst according to claim 15 furthercomprising the step following said calcining step, of activating saidcatalyst by treating the calcined particles under conditions sufficientto convert the iron oxide to at least one iron carbide.
 22. A processfor producing hydrocarbons comprising the steps: contacting syngas withan attrition resistant bulk iron catalyst comprising substantiallyspherical particles, said particles comprising a finely divided ironcomponent and a substantially uniformly distributed binder, said ironcomponent being selected from the group consisting of iron oxideprecursors, iron oxide derivatives of said iron oxide precursors andcatalytically activated iron derivatives of said iron oxide precursors,said iron component being present in an amount, calculated as Fe₂O₃, ofat least 50 wt. %, said catalyst having an attrition loss after one houras determined by ASTM D-5757-95 of less than about 15 wt. % based onactual catalyst weight, and recovering a product stream comprising atleast one hydrocarbon.
 23. The process of claim 22 wherein saidcontacting step is conducted in a slurry bubble column reactor.
 24. Theprocess of claim 23 wherein said syngas has a H₂/CO ratio of less than1.0.
 25. The process of claim 24 wherein said hydrocarbon in saidproduct stream comprises wax.
 26. A process for producing hydrogen fromcarbon monoxide and steam comprising the steps: contacting a feedcomprising carbon monoxide, steam, and optionally hydrogen, with anattrition resistant bulk iron catalyst comprising substantiallyspherical particles, said particles comprising a finely divided ironcomponent and a substantially uniformly distributed binder, said ironcomponent being selected from the group consisting of iron oxideprecursors, iron oxide derivatives of said iron oxide precursors andcatalytically activated iron derivatives of said iron oxide precursors,said iron component being present in an amount, calculated as Fe₂O₃, ofat least 50 wt. %, said catalyst having an attrition loss after one houras determined by ASTM D-5757-95 of less than about 15 wt. % based onactual catalyst weight, and recovering a product having an increasedhydrogen content as compared to said feed stream.
 27. The process ofclaim 26 wherein said contacting step is conducted in a slurry bubblecolumn reactor.
 28. The process of claim 27 wherein said feed has aH₂/CO ratio of less than 1.0.